The invention relates to a soldering workpiece made from aluminum and/or aluminum compounds, to a soldering process and to a heat exchanger soldered in this manner.
To join two metallic workpieces by means of a soldered join, it is necessary for the oxide layer formed at the surfaces of the workpieces to be at least partially removed prior to the soldering operation and not to be formed again during the soldering process. This is generally achieved using special soldering agents for metal oxides, known as fluxes. At present, for example for the brazing of aluminum components for heat exchangers, as are used in the automotive industry, it is customary to use special soldering processes, in particular what is known as the “Nocolok” soldering process using fluxes based on potassium fluoroaluminates.
Even the application of the fluxes is often very complex and expensive. Furthermore, the components are covered with fluxes after the soldering operation, often requiring complex cleaning treatment and/or other surface treatments following the soldering process in order to meet industry requirements for desired properties of components, such as corrosion-resistant, hydrophilic and/or bonding surfaces and/or to comply with aspects such as cleanness, product design or appearance. For example, the flux which is commercially available under the trade name “Nocolok” remains on the surface after the soldering of aluminum components, covering it with a crystalline layer which has to be subjected to further cleaning and conversion treatments depending on the intended use. Moreover, the use of fluxes has an adverse effect on the environment and the equipment and machines used, which are exposed to high levels of wear, causing a short service life. Furthermore, it becomes more difficult to use materials containing zinc and/or magnesium, since the zinc or magnesium reacts with the flux, thereby increasing the consumption of flux and affecting the materials properties.